Development of the low temperature curing type paints for the cast wheel

摘要

In the cast wheels for motorcycles, both of the top and bottom faces with different solidifying speed at casting present the external appearance and design surfaces and the top faces are often marked with casting defects. One of the causes of high fraction defective in painting is because the casting defects in pinhole state appearing to the surface cause the bulging of paint during the stage of baking paint. In the current development, to realize the baking process at under 80°C, acrylic silicon paint for building materials possible of drying at normal temperature was used as the base material and paint suited for cast wheels was developed by optimizing curing catalyst and the molecular weight of paint resin. The development made it possible to switch the conventional baking process performed at 140°C to the drying process at 60°C and reduce the fraction defective by 20% as well as the amount of VOC used by 20%.